Flow simulation and diaganosis through hydraulic turbines using a RNG k-�� turbulence model

Francis turbine is widely employed in large scale hydropower stations in the world with main characteristics of efficiency, stability and cavitation. In practical establishment, each large power station must develop a new Francis turbine for its special natural condition and requirement, such as higher efficiency for utilization of natural resources. CFD has been developed greatly and helped a lot in hydraulic design stage of the turbine. In this paper, firstly, a new RNG k -?? turbulence model is proposed based on the RNG k -?? model, which brings the nonlinear term of the mean fluid flow transition to the ?? equation in the original k -?? model. And, this RNG k -?? model has been used to predict the energy performances for Francis turbine. Then, the flow diagnosis method in the turbine runner based on vorticity parameters is presented, following the detailed flow behavior revealed. Finally, the simulation results for different model Francis turbines have been compared and analyzed for optimizing the energy performances of the turbine. The model test results indicate that the efficiency of hydraulic turbine has been improved from 93.6% to 94.5%. Copyright ? 2010 by ASME.EI